154 THE CYTOLOGY AND LIFE-HISTORY OF BACTERIA 



It is readily demonstrable that the spore-nucleus is in a condition of turgour, 

 and these pieces of evidence, taken in conjunction with the exceedingly small 

 relative size of most spores, and the resistance to denaturation of their proteins, 

 suggest very strongly that the spore is reduced in size and weight by reduction 

 of water-content, as an adaptation to aerial distribution, and that its resistance 

 to heat and antiseptics follows as a consequence, indeed as a by-product of 

 this process. 



Previous concepts of the nature of spores have been based upon information, 

 much of which is incomplete, and some definitely misleading. In the latter 

 category, the theory that sporulation takes place in response to the stimulus 

 of an unfavourable environment is so completely exploded as to require no 

 further comment. But a less obvious misconception, arising from a failure to 

 realise that more-or-less spore-like resting cells are of universal occurrence 

 among bacteria, is the belief that spores are especially resistant to the processes 

 of inanition, that is to say, of oxidation, which is the main cause of death in 

 resting cells. Obviously spores arc more resistant than the corresponding 

 vegetative cells, but there is no evidence at all to suggest that they are more 

 so than the resting cells of non-sporing bacteria ; and this is the true com- 

 parison. It is a commonplace of practical bacteriology that bacteria dried 

 iti vacuo will survive indefmitely. 



This is a crucial point in the argument. If spores were more resistant than 

 microcysts to inanition, then their possession would confer a most decided 

 advantage, and no other explanation of their existence would be required. 

 But the agencies to which spores are, in fact, especially resistant are most 

 unlikely to be encountered under natural conditions, and, it they were, this 

 resistance would confer little or no genetic advantage since the spore can 

 neither metabolise nor reproduce. It may survive indefmitely in a hot spring, 

 but evolve it cannot. 



Previous theories have attempted to account for the spore in terms of its 

 importance, not to the bacillus but to the bacteriologist, and the comparisons 

 which have been made have not been true ones. 



Whereas the aerobic genus Bacillus comprises a wide variety of specific 

 types, retaining the relatively tiny spore, and capable of profiting by aerial 

 distribution ; in the much smaller genus Clostridiiiiii, which by the genetic 



